Abstract
Bone loss can be treated in one of two general ways. Missing bone can be replaced either with bone graft applied to the host bone or augmentations attached to the revision implants. The ideal treatment of bone defects during revision TKR surgery: 1) makes immediate full weight bearing possible; 2) provides longterm support for the implants; 3) Restores original bone stock.
Bone grafts achieve these goals when the defects are CAVITARY. Therefore, bone grafts rather than metal augmentation devices are the surgical treatment of choice when these types of defects are encountered during revision TKR surgery.
Although bone grafts may achieve these goals when the defects are SEGMENTAL, the results are uncertain and more difficult to achieve. Metal augmentations make possible immediate full weight bearing and provide reliable long-term support for revision TKR implants. When these augments are made of Tantalulm, a metal with 80% porosity, the restoration of bone stock is also possible.
There are advantages and drawbacks to each approach. The advantages of bone grafts are that they: 1) restore bone stock; 2) are relatively inexpensive (especially if autogenous graft is used); 3) can be applied with relatively simple instrumentation; and 4) allow defects of a wide variety of sizes and shapes to be treated. The disadvantages of bone grafts are that they: 1) have limited application in large, segmental defects where structural support is necessary; 2) do not always unite predictably, particularly when the host bone is osteopenic or when angular deformities exist; 3) are shaped and inserted without the benefit of precise instrumentation; and 4) may require limited weight bearing or restricted activity for a period of time following surgery. The advantages of augmentation devices are that they: 1) can be manufactured in a wide variety of shapes and sizes; 2) provide immediate stable fixation; and 3) can be inserted using precise cutting instruments. Therefore, the indications for metal augmentation devices are: 1) uncontained defects (segmental) that require structural support for the knee implant; 2) knees with osteopenic bone or large angular defects; and 3) older patients in whom the importance of immediate mobilization and unrestricted weight-bearing is more important than the restoration of bone stock.
The abstracts were prepared by Mrs Dorothy L. Granchi, Course Coordinator. Correspondence should be addressed to her at PMB 295, 8000 Plaza Boulevard, Mentor, Ohio 44060, USA.
